4*3/2=6 (unit)
That is, after improving efficiency, six machines can be installed every day.
According to the meaning of the question: (2/3 * x)/4+(1/3 * x)/6 = (1/4 * x)-1.
That is, the time to install 2/3 machines under the original efficiency plus the time to install 1/3 machines after improving efficiency is one day less than originally expected.
Solution: x=32, x/4=8.
A: This batch of 32 machines is expected to be completed in 8 days.